CYP2D6 and myopathy: Homozygous CYP2D6 mutations result in increased levels of simvastatin, thereby predisposing patients to statin-induced myopathy.7 Abiraterone is an inhibitor of CYP2D6 in addition to being a substrate for CYP3A4.8 Under normal conditions, CYP3A4 activity is adequate and both drugs can be used concomitantly.